The present invention relates to battery chargers for recharging storage batteries, and especially to a charger for industrial batteries of relatively high capacity such as are used, for example, in mine cars and industrial trucks.
Such batteries may have different capacities depending on their intended use, and are, therefore, available in a relatively large number of standard ampere-hour ratings extending over a considerable range and which may be as high as 800 ampere-hours or more, for example. Such batteries, even when fully discharged, must be completely charged within a time period of not over eight hours, so that the battery can be put on charge at the end of a working shift and will be ready for use again at the end of the next shift. This requires a charger, preferably automatically controlled, that can maintain the charging rates on a preset cycle such that the battery will be fully charged within the required time but not overcharged.
As indicated above, these batteries may be rated at any ampere-hour capacity extending over a wide range. In addition, the number of cells in the battery may vary depending on the desired battery output voltage. It has been considered necessary, therefore, to design battery chargers for this type of service so that they could be adjusted for the different possible ampere-hour ratings and for different numbers of cells. That is, adjustments have been provided so that the maximum and minimum charging currents could be set to different values for batteries of different ratings such that the currents had fixed relations to the rating, the current usually being a predetermined percentage of the ampere-hour rating. Batteries are also usually available with at least two different numbers of cells, depending on the desired voltage, and adjustments have also been provided to adjust for the number of cells so that a desired constant voltage per cell could be maintained.
These adjustments were, of course, provided to enable a given battery charger to be used to charge different batteries of different ratings and number of cells. In practice, these adjustments were usually made at the factory by the manufacturer of the charger since battery chargers are usually purchased for use with a specific size of battery. In some cases, however, the adjustment may be made by the user if a change is made to batteries of a different rating. The provision of adjustments of this kind in an otherwise standard battery charger has represented an undesirable complication and an added cost. The presence of these adjustments also involves the risk that the user might attempt to make adjustments when they are not needed, as the charger would normally have been correctly set initially. If a change of adjustment should be required, it might be made incorrectly, or the user could fail to make an adjustment when it should have been made. Either of these possibilities could have serious, or at least undesirable, consequences. The necessity of providing adjustments of this kind in battery chargers has, therefore, been undesirable but they have heretofore been considered necessary.